add info line saying TLJH setup complete

[raybellwaves]

When looking at the logs i'm not sure when the setup has finished as the last line is logger.info("Running TLJH installer..."). This PR adds the line logger.info("TLJH setup complete") so myself and others know we can go have fun

[raybellwaves]

I also see in opt/tljh/installer.log

2021-12-17 04:31:59,773 Waiting for JupyterHub to come up (1/20 tries)
2021-12-17 04:31:59,788 Done!

in the logs so this may not be needed

[consideRatio]

The added code is unreachable because of the call to os.execv:

These functions all execute a new program, replacing the current process; they do not return. On Unix, the new executable is loaded into the current process, and will have the same process id as the caller. Errors will be reported as OSError exceptions.

From https://docs.python.org/3/library/os.html

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I also see in opt/tljh/installer.log

2021-12-17 04:31:59,773 Waiting for JupyterHub to come up (1/20 tries)
2021-12-17 04:31:59,788 Done!

in the logs so this may not be needed

Excellent, closing!